INVESTIGATING THE NATURE AND TIMING OF THE EARLIEST HUMAN OCCUPATION OF NORTH AMERICA USING A NOVEL INTEGRATION OF BIOGEOCHEMISTRY AND MICROMORPHOLOGY

人们是如何、何时和为什么第一次来到美洲定居的？这个谜题激发了科学和公众的想象力，也是持续辩论的主题。“克洛维斯第一”的传统模式认为，克洛维斯文化是在公元前13,500年左右到达美洲大陆的，克洛维斯文化是以20世纪20年代和30年代在新墨西哥州克洛维斯附近发现的独特石器命名的。这些人会穿越西伯利亚的贝林贾大陆桥，当时海平面在上一个冰河时代降低，最终在落基山脉东侧向南移动。最近，越来越多的证据表明了一个更复杂的过程，可能有几波不同文化群体的迁徙。这导致了一种情况，即对于人类最初是如何来到美洲的，没有达成共识。解决这一争论的主要障碍是缺乏保存完好的遗址和容易断代的材料，在这些材料中，我们可以确定我们正在约会的东西确实代表了人类的存在。这一时期的人类骨骼遗骸特别罕见，而且由于1990年美国原住民坟墓保护和遣返法案(NAGPRA)的限制，研究也非常困难。然而，一种更不寻常的考古证据在洞穴中保存得很好：人类粪便化石，或粪便化石。最著名的史前粪岩之一，是来自俄勒冈州佩斯利洞穴的标本，年代为14,300年前；比克洛维斯文化的证据早1000年。这块榴辉岩是“前克洛维斯”占领北美的有力证据。根据古代DNA，该榴辉岩被确认为人类，但对于地层的完整性一直存在争议。这是一个继续在这一领域进行大量研究的问题。我们根本不知道这些分子在洞穴沉积物中的移动程度。这是缺少的科学环节，阻止了粪便被毫不含糊地用于证实前克洛维斯假说和解决这场旷日持久的辩论。我们的研究将首次尝试通过使用生物地球化学和沉积物微形态的新集成来解决这些问题--这是PI和Co-I成功开发的一种方法。沉积物微形态可以看作是显微镜下的挖掘。完整的考古沉积物块被镶嵌在树脂中，并变成幻灯片，在显微镜下观看。通过这种方式，我们可以直观地检查沉积物的沉积过程，以及它们是否随后发生了变化。结合粪便脂质的生物地球化学分析，将使我们能够量化这些分子从它们的沉淀点移动的程度。我们将结合特定化学组份的放射性碳测年来进行这一分析--我们不会测定样品中所有的有机物质的年龄，而是测定粪岩中的个别化学组份的年龄。通过这种方式，我们可以提供一个确切的物种鉴定，同时提供一个明确的粪石沉积日期。无论这些早期定居者是谁，这些他们留下的不太可能的证据来源包含了丰富的信息，我们现在可以使用这项研究项目中提出的新技术来获取这些信息。一旦我们能够证明在洞穴中发现的骨灰岩材料的完整性，并因此对我们从他们那里获得的科学数据有信心，我们就可以使用与骨灰石一起保存的分子和化石来重建这些人的饮食和他们居住的环境。通过将其与高分辨率放射性碳测年相联系，我们可以开始扩展研究潜力，以研究其他具有科学和考古意义的问题，如洞穴使用的季节性；这些早期定居者与环境有什么关系，以及他们如何利用可用的资源？

How, when and why did people first arrive and settle in the Americas? This puzzle is one that has captured scientific and public imagination, and is the subject of continued debate. The traditional model of 'Clovis First' asserts that the Clovis culture, named after their distinctive stone tools found near Clovis, New Mexico, in the 1920s and 1930s, arrived on the continent around 13,500 BP. These people would have travelled across the Beringia land bridge in Siberia, during a time when sea levels were lowered during the last ice age, and eventually made their way south on the east side of the Rocky Mountains. Recently a growing body of evidence points to a more complex process, with perhaps several waves of migration of different cultural groups. This has led to a situation where there is no consensus on how humans first came to the Americas. The main barrier to addressing this debate, is the scarcity of well-preserved sites and easily datable materials, where we can be sure that what we are dating really does represent human presence. Human skeletal remains from this period are especially rare, and also incredibly difficult to study due to restrictions of the Native American Graves Protection and Repatriation Act 1990 (NAGPRA). However, a more unusual form of archaeological evidence are well preserved in caves: fossilized human faeces, or coprolites. One of the most famous prehistoric coprolites, is a specimen from Paisley Caves, Oregon, dated 14,300 BP; one thousand years earlier than evidence from the Clovis culture. This coprolite is strong evidence for the 'Pre-Clovis' occupation of North America. The coprolite was identified as human on the basis of ancient DNA, but there have been debates over the stratigraphic integrity. This is a problem which continues to underlie much research in this area. We simply do not know the extent to which these molecules are mobile within cave sediments. This is the missing scientific link which prevents the coprolites from being used, unambiguously, to confirm the pre-Clovis hypothesis and solve this long running debate. Our research will make a first attempt to address these problems, by using a novel integration of biogeochemistry and sediment micromorphology - a method successfully developed by the PI and Co-I. Sediment micromorphology can be thought of as an excavation under the microscope. Intact blocks of archaeological sediments are set in resin and turned into slides for viewing under a microscope. This way we can visually examine the processes by which sediments have been deposited, and whether they have been subsequently altered. Combining this with biogeochemical analysis of faecal lipids will enable us to quantify the extent to which these molecules move from their point of deposition . We will conduct this analysis in conjunction with radiocarbon dating of specific chemical fractions - rather than dating all the organic material in a sample, we will date individual chemical fractions within the coprolites. This way we can provide a firm species identification, and simultaneously an unambiguous date for when the coprolite was deposited. Whoever these early settlers were, these unlikely sources of evidence that they left behind contain a wealth of information which we can now access using the novel techniques proposed in this research project. Once we can demonstrate the integrity of the coprolite materials found in the cave and therefore have confidence in the scientific data we obtain from them, we can use the molecules and fossils preserved with the coprolites to reconstruct the diets of these individuals, and the environment they inhabited. By linking this with high resolution radiocarbon dating, we can begin to extend the research potential to look at other questions of scientific and archaeological interest such as the seasonality of cave use; what relationship did these early settlers have with the environment, and how did they utilise the resources available to them?